Remove unnecessary delays. There is no reason to wait after each and every

Remove unnecessary delays.  There is no reason to wait after each and every
read or write to aregister.  There is also no reason to wait after
transmitting a STOP since the controller will wait until the bus is free
when transmitting the next START.  Based on a diff by Stephen Graf.

Also remove the interrupt code; it doesn't work on the newer variants of
the device.  The functionality will be put back in a future commit.

ok patrick@